Because of the scientific and technological progress and the increase of the living standard, water taking devices for facilitating the use of water dispensers emerge continuously. To solve the problem on directly vertical extraction of barreled water for drinking and avoid secondary pollution caused by the use of the water dispensers, an disclosure patent No. CN202873028 disclosed on Jan. 28, 2015 relates to a hand pump used for barreled water. The hand pump includes a base, a water pumping pipe mounted below the base, and a water discharging pipe located on the side of the base, and is characterized in that an upper end of the base is connected with a pump shell. An air drum is disposed in the pump shell. An air drum seat is disposed at the lower end of the air drum. An air feeding seal and an air discharging seal are disposed in the air drum seat. A gland is disposed at the upper end of the air drum. The hand pump occupies a small space, is convenient to carry and mount, and is convenient for water pumping. The gland is operated vertically, and spring return handfeel is strong. By full use of an air bag of the air drum, a force applied to the air drum is relatively low, so that the hand pump is suitable for people of all ages. When the hand pump is not used, water is in no contact with a pump body, so that no secondary pollution is caused to the barreled water. A fixed seat at the lower end of the base is connected and matched with a barreled water bucket opening. However, not all barreled water bucket openings are in same size. If the size of the bucket opening is smaller than a size of the fixed seat, the sealing reliability would be reduced. If the size of the bucket opening is larger than the size of the fixed seat, requirements for stable connection and successful water taking may not be met.